The present invention relates generally to bonding together metals and, more particularly, to an agent and method for pre-treating the surfaces of the metals to be bonded together, when the metals are bonded together with the use of polymer adhesives.
As compared with bonding together base metals such as cobalt, chromium, nickel, titanium, iron and copper as well as their alloys, it is much more difficult to bond together chemically stable noble metals such as gold, platinum and palladium as well as noble metal alloys containing them as main components; that is, there is no or little technique to meet such demands.
In an effort to improve the adhesion of noble metals, applying primers on them, sandblasting their surfaces by physical means, tinning and oxidizing them have been proposed so far in the art. Of these procedures, the application of primers is the simplest one. Typical primers comprise monomers containing 6-(4-vinylbenzyl-n-propyl)amino-1,3,5-triazine-2,4-dithion (VBATDT), as set forth in Japanese Patent Application Laid-Open No. 64-83254 and thiophosphoric acid, as referred to in Japanese Patent Application Laid-Open No. 1-138282.
Some of the procedures mentioned above are found to be effective under dry conditions, but have the disadvantage of being poor in water resistance and durability. The application of primers, on the other hand, is considered preferable because of being free from such problems.
However, problems with using VBATDT as a primer are that some limitation is placed on what metals are bonded together and what catalysts are used for curing the bonding agent as well. It is admitted that the procedure of using a monomer containing a thiophosphoric acid group has some effect, but it offers storing and handling problems because the material is unstable.
A primary object of this invention is therefore to provide a pre-treatment or primer agent which can be used with every metal and every catalyst for curing adhesives and does not pose any storing and handling problems.